Over the past two decades, increasing levels of dissolved organic matter (DOM) have been observed in inland waters throughout the northern hemisphere. This poses a challenge to drinking water treatment plants in that DOM serves as organic precursors to harmful byproducts, such as haloacetic acids (HAAs), produced during chlorine-based disinfection. Thus, understanding the chlorine reactivity of the DOM pool of a particular water source becomes fundamental for any utility. In this study, the formation kinetics of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two most prevalent HAA species, were delineated upon chlorination of seventeen aliphatic and aromatic DOM precursors and sixty-eight inland lake waters sampled across the upper Midwest region. A comparative approach built upon the hierarchical cluster analysis of combined DCAA and TCAA kinetic datasets was developed to display similarities and uncover differences the among model DOM precursors and water samples based on the notion of proximity measure. One key finding was that the apparent DCAA and TCAA formation rate constants could be grouped into four statistically different clusters reflecting the structural features of model precursors, including non-�-diketone aliphatics, �-diketone aliphatics, non-�-diketone phenolics, and �-diketone phenolics. Furthermore, photobleaching treatment and long-term dark incubation shifted the clustering patterns of water samples, suggesting that aquatic processing altered the character and reactivity of DOM prior to chlorination. Our results demonstrate the suitability of an integrated kinetic-statistical method for qualitative evaluation of the chlorine reactivity of HAA precursors, which may complement the formation potential test conventionally used for source water quality monitoring.

Mapping chlorine reactivity patterns of haloacetic acid precursors in inland lakes of the upper Midwest, USA

248th National Meeting (2014)

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